text: Transition metal and main group compounds often react differently. The important role of d-orbitals in bonding strongly influences the pathways and rates of ligand substitution and dissociation.  These themes are covered in articles on coordination chemistry and ligand.  Both associative and dissociative pathways are observed.
  An overarching aspect of mechanistic transition metal chemistry is the kinetic lability of the complex illustrated by the exchange of free and bound water in the prototypical complexes [M(HO)]:
  :[M(HO)]  + 6 HO*  →  [M(HO*)]  +  6 HO
  :where HO* denotes isotopically enriched water, e.g., HO
  The rates of water exchange varies by 20 orders of magnitude across the periodic table, with lanthanide complexes at one extreme and Ir(III) species being the slowest.